Solve for $x$ and $y$ using substitution. ${-3x-3y = -12}$ ${y = -2x+9}$
Explanation: Since $y$ has already been solved for, substitute $-2x+9$ for $y$ in the first equation. ${-3x - 3}{(-2x+9)}{= -12}$ Simplify and solve for $x$ $-3x+6x - 27 = -12$ $3x-27 = -12$ $3x-27{+27} = -12{+27}$ $3x = 15$ $\dfrac{3x}{{3}} = \dfrac{15}{{3}}$ ${x = 5}$ Now that you know ${x = 5}$ , plug it back into $\thinspace {y = -2x+9}\thinspace$ to find $y$ ${y = -2}{(5)}{ + 9}$ $y = -10 + 9$ $y = -1$ You can also plug ${x = 5}$ into $\thinspace {-3x-3y = -12}\thinspace$ and get the same answer for $y$ : ${-3}{(5)}{ - 3y = -12}$ ${y = -1}$